When to Get Tested?

When you have symptoms of arthritis-like chronic joint pain, stiffness, and inflammation in certain areas of your body, such as your lower back, hips, neck, and chest, or have painful inflammation of the eyes called uveitis, especially if you are male and the symptoms began in your early 30s

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

HLA-B27 is a specific protein (termed a human leukocyte antigen or HLA) that is found on cell surfaces. The term HLA-B27 is also used to refer to the gene that codes for the HLA-B27 protein. The HLA-B27 test determines the presence or absence of HLA-B27 protein on the surface of a person's white blood cells.

Human leukocyte antigens are proteins that help the body's immune system identify its own cells and distinguish between "self" and "nonself." Everyone has an inherited combination of HLA genes that code for the many antigens present on the surfaces of their cells. The presence or absence of each antigen creates a distinctive HLA combination for each person.

While HLA-B27 has not been established as a cause of any of these disorders, there is a higher prevalence of the antigen in those affected. For example, even though only 6% of the population has HLA-B27, approximately 88% of people with ankylosing spondylitis are positive for HLA-B27.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Ankylosing spondylitis and reactive arthritis are both chronic, progressive conditions that occur more frequently in men than women. The first symptoms typically occur when a person is in their early 30's. Often, the initial symptoms of these autoimmune disorders are subtle and may take several years before characteristic degenerative changes to bones and joints are visible on X-rays.

Ankylosing spondylitis is characterized by pain, inflammation, and a gradual stiffening of the spine, neck and chest.

Reactive arthritis is a group of symptoms that includes inflammation of the joints, urethra, and eyes as well as skin lesions.

Juvenile rheumatoid arthritis is a form of arthritis that occurs in children.

Anterior uveitis is associated with recurring inflammation of the structures of one or both eyes.

The HLA-B27 test may be ordered as part of a group of tests used to diagnose and evaluate conditions causing arthritis-like chronic joint pain, stiffness, and inflammation. This group of tests may include an RF (rheumatoid factor) with either an ESR (erythrocyte sedimentation rate) or a CRP (C-reactive protein). HLA-B27 is sometimes ordered to help evaluate someone with recurrent uveitis that is not caused by a recognizable disease process.

When is it ordered?

An HLA-B27 test may be ordered when a person has acute or chronic pain and inflammation in the spine, neck, chest, eyes, and/or joints, and the doctor suspects the cause is an autoimmune disorder that is associated with the presence of HLA-B27. An HLA-B27 may also be ordered when someone has recurrent uveitis.

The HLA-B27 test is not diagnostic, but the results add information, increasing or decreasing the likelihood that the person being evaluated has the suspected autoimmune disorder.

Doctors frequently use the HLA-B27 test result when they suspect ankylosing spondylitis but the disease is in an early stage and the vertebrae in the spine have not yet undergone the characteristic changes that would be seen on X-ray.

What does the test result mean?

If a person is positive for HLA-B27 and has symptoms such as chronic pain, inflammation, and/ or degenerative changes to his bones (as seen on X-ray), then it supports a diagnosis of ankylosing spondylitis, reactive arthritis, or another autoimmune disorder that is associated with the presence of HLA-B27. This is especially true if the person is young, male, and if he experienced his first symptoms before the age of 40.

If HLA-B27 is negative, then the marker was not detected. This does not mean, however, that the person tested does not have the suspected condition since people who do not have the HLA-B27 antigen can also develop these autoimmune diseases. Likewise, someone who has the HLA-B27 antigen will not necessarily develop one of these conditions. Researchers are trying to determine what factors contribute to the higher likelihood of people with HLA-B27 developing these particular diseases and what actually triggers them.

Whether or not certain HLA antigens will be present is genetically determined. Their production is controlled by genes that are passed from parents to their children. If two members of the same family are HLA-B27 positive and one of them develops a disease associated with HLA-B27, then the other person is at an increased risk of developing a similar disease.

Is there anything else I should know?

Though the diseases associated with HLA-B27 occur more frequently in men, women can also be affected. However, the signs and symptoms related to the diseases can often be milder in women.

With new genetic testing methods, it is now possible to separate HLA-B27 into subtypes. So far, more than 70 different subtypes have been identified, such as HLA B27*05 and HLA B27*02. How the presence of these specific subtypes affects the likelihood of developing an autoimmune disease is not yet known.

Common Questions

1. What causes the autoimmune disorders associated with HLA-B27?

In most cases, the cause is not known. However, in some cases of reactive arthritis, there is an association between a previous infection by a microorganism, such as Chlamydia, Campylobacter, Salmonella, Ureaplasma, or Yersinia, and the onset of the disease. It is thought that similarities between the HLA-B27 antigen and the antigens found on the surface of the microorganisms trigger the immune system to fight both the microorganism and the person's own tissues, launching the autoimmune disorder after the resolution of the infection.

2. Can I be tested for HLA-B27 in my doctor's office?

HLA-B27 testing requires specialized equipment and expertise to perform. It is not typically performed in a doctor's office and is not offered by every laboratory. In most cases, your blood sample will be sent to a reference laboratory.

3. Should everyone have an HLA-B27 test done?

Routine testing of the general public is not recommended. Usually only those with symptoms will be tested. A positive HLA-B27 in a person who does not have symptoms or a family history of HLA-B27-associated disease is not clinically significant. It does not help predict the likelihood of developing an autoimmune disease. Occasionally, a family member of a person who is positive for HLA-B27 and has an autoimmune disorder may be tested, but the test result cannot be used to predict whether the tested person will develop a related autoimmune disease.

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Article Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Thjodleifsson, B. et. al.(2007 July 30). Evidence of a Common Genetic Background for Ankylosing Spondylitis and Inflammatory Bowel Disease. American College of Rheumatology from Arthritis & Rheumatism 2007; (DOI:10.1002/art.22812) [On-line journal article]. Available online at http://www.rheumatology.org/press/2007/0730ankylosing.asp through http://www.rheumatology.org. Accessed on 9/09/07.

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This article was last reviewed on July 10, 2013. | This article was last modified on July 10, 2013.

The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.

The modified date indicates that one or more changes were made to the article. Such changes may or may not result from a full review of the article, so the two dates may not always agree.